The present invention relates to semiconductor device manufacturing techniques, specifically fabrication of through silicon vias (TSVs) with multiple diameters.
In the electronics industry, packaging density continuously increases in order to accommodate more electronic devices into a package. In this regard, three-dimensional (3D) stacking technology of wafers and/or chips contributes to the device integration process. Typically, a semiconductor wafer (a semiconductor device/substrate) or chip (a semiconductor device) includes several layers of integrated circuitry (e.g., processors, programmable devices, memory devices, etc.) built on a silicon substrate. A top layer of the wafer may be connected to a bottom layer of the wafer through silicon interconnects or vias. Typical vias include metallic material formed in cavities in the semiconductor that electrically connect conductive contacts disposed in different areas of a device. In order to form a 3D wafer stack, two or more wafers are placed on top of one other and bonded together.
Previous methods for electrically connecting the wafers used vias that consumed geometric space on the wafers or chips by connecting multiple vias of a single diameter utilizing additional wiring levels. Alternately, the formation of TSVs with complex shapes, such as multiple diameters in a single TSV, used inefficient fabrication methods utilizing additional mask layers and patterning steps, which added cost, complexity, and process time to the manufacturing process.